This invention relates generally to ribbon cartridges for use in typewriters and/or printers employed in word processors, line printers and the like and more particularly to a ribbon tensioning device for use in such a cartridge which minimizes the spilling of the ribbon as it is transferred from a supply spool onto a takeup spool.
Ribbon cartridges containing inked ribbons used in typewriters and/or printers are conventionally of the type wherein the ribbon is of the single pass variety, i.e. it is not reuseable as in the case of the older type ink impregnated cloth ribbons. During use, the ribbon passes only once through the cartridge from a supply spool to a takeup spool. After the ribbon has been transferred to the takeup spool, the cartridge is discarded and replaced with a fresh one.
Cartridges of the type described which are presently available are for the most part satisfactory in operation, however, there is the tendency for the ribbon to spill from the supply spool in the cartridge after a quantity of the ribbon has been wound onto the takeup spool. It is thought that the tension on the ribbon is reduced below that which is necessary to maintain the ribbon properly on the spools. In time, this can cause a jamming of the ribbon in the cartridge. If this occurs, it becomes necessary to replace the cartridge prior to making use of all the ribbon therein. This wastes ribbon and increases the cost thereof to the user.
It has been found that to prevent or at least minimize the spilling of ribbon in cartridges of the type described, a substantially uniform tension on the ribbon is required during movement of the length of the ribbon in the cartridge from the supply to the takeup spool. In some cases, ribbon lengths may be as great as 500 feet and as such this becomes a rather difficult task.
To overcome this problem, tensioning belts and brake devices have been employed in such ribbon cartridges in an attempt to provide a uniform tensioning of the ribbon during playout. The belts while improving the situation somewhat, have not provided a satisfactory solution to the problem. When the belts are used, a decrease in tension nevertheless occurs as the ribbon is played out and as such spilling may result. In the case of the spool brakes, too great a tension can be placed on the ribbon as it is played out and as such the ribbon may break.
In other fields of technology related somewhat to ribbon cartridges, individual leaf spring brake arms have been provided in magnetic tape cartridges to provide a tensioning on the magnetic tape as it is transferred between a pair of spaced spools. The brake arms function independently and as such would appear to apply a decreasing tension on the supply spool as the magnetic tape is played out therefrom and an increasing tension on the takeup spool as the magnetic tape is taken up thereon. Consequently, this type of arrangement if applied to a ribbon cartridge would not be satisfactory to provide the necessary uniform tension required throughout the transfer of the ribbon so as to minimize the spilling of the ribbon from the ribbon spools. Other over-center or toggle spring devices have been used in magnetic tape cartridges as well to prevent unspooling or entangling of the tape while the tape is being rewound. These devices likewise would not suffice to provide a proper uniform tension in a ribbon cartridge for a typewriter or printer in which the ribbon passes only once from a supply spool to a takeup spool during operation thereof.